The European patent 1143966 B1 describes the use of a preparation comprising formic acid as an active ingredient for the manufacture of a medicament for the treatment of warts caused by virus in a mammal, by topical administration of the medicament on the affected area. The patent teaches that the wart should be softened with hot water and that, if necessary, hard skin covering the wart should be scraped of, before treatment with formic acid.
Bhat et al. (“Topical formic acid puncture technique for the treatment of common warts”, International Journal of Dermatology 2001, 40, 415-419) discloses a topical application/needle puncture technique for the treatment of warts.